Emulsion coating systems generally contain emulsifiers which prevent the emulsion phase from separating out of the liquid vehicle prematurely. Practitioners have generally tried to avoid such premature phase separation as it is important for the emulsion to remain intact until after application of the system to a substrate to form acceptable coatings. Thus after the emulsion has been applied to the substrate, the liquid vehicle (water plus co-solvents) is usually volatized to leave the emulsion phase as a residual coating. Generally, this volatilization of the liquid vehicle requires lengthy drying times and/or elevated temperatures to form the film coating. Therefore, to reduce processing times when emulsion coating systems have been used, tremendous amounts of energy are required to reduce drying times. Otherwise, process times are greatly increased while the coating dries.
Emulsion coating systems are used in many industrial processes. Such processes include metal coatings, such as airplane coatings, transportation vehicle coatings, tank coatings, pipe coatings; foam coatings, asbestos abatement, and decorative panels and walls. While traditional volatilization of the liquid vehicle is satisfactory in many emulsion coating systems, the speed of useful coating formation is crucial in some coating uses. Therefore, a tough, quick-forming coating is needed which can allow the rapid reuse of a work piece or workplace after the coating is applied.
Asbestos abatement is one particular area in which the use of emulsion coating systems is growing. Asbestos has long been used for thermal insulation, particularly for high temperature surfaces or where fire proofing is required. Examples of such applications include heating plant equipment such as furnaces, boilers, steam lines, etc. Many times, this equipment is located in confined regions such as building crawl spaces, tunnels, and storage areas which have dirt floors.
With the discovery of the dangers involved in airborne, particulate asbestos, much concern has been directed to the removal and sealing of asbestos from the workplace. This is especially difficult in areas having a dirt floor as, over the years, significant amounts of particulate asbestos may have fallen to the dirt floor and become incorporated into the soil. As this soil is disturbed, the particulate asbestos can often become airborne.
Two approaches have been used to address this problem. First, the top 1-6 inches of the soil may be collected and removed. This approach requires the removal of large amounts of dirt and the handling and disposal of a hazardous substance, which is expensive.
A second approach has been to encapsulate the asbestos particles within the soil, sealing the asbestos contaminated soil from the environment. A number of formulations have been made available for this purpose. U.S. Pat. No. 4,702,861 to Farnum discloses a flame retardant formulation which may be utilized to coat or encapsulate layers of in-place asbestos. These formulations have binding and particle wetting capabilities which help it to bind and seal asbestos fibers in place. The formulation is based on an aqueous latex dispersion of polyvinylchloride-acrylic copolymer together with certain other film forming and viscosity-controlling components. This formulation appears to be intended for use in coating rigid equipment and structures. Its use in sealing deformable surfaces is not discussed, and there is no 5 indication it has the bridging strength to do so.
The "SPEC-DATA.RTM." sheet regarding SERPAFLEX SHIELD.TM. Encapsulating Sealant, International Protective Coatings Corp., May 1988, discloses a water base acrylic vinyl copolymer coating used to seal sprayed asbestos insulation, fire proofing, and used as a pipe and boiler lagging.
U.S. Pat. No. 4,866,105 to Batdorf discloses an encapsulant having superior wettability and low viscosity for use in asbestos containing material removable. This encapsulant comprises a latex, a nonionic surfactant and a cationic surfactant for the improved wettability of the encapsulate, and it is intended for use on a structural unit.
U.S. Pat. No. 4,477,490 to Weisberg addresses some of these problems. This patent discloses a two-step process for encapsulating asbestos fibers in a silicate polymer and coating the encapsulated fibers with an abrasion-resistant and impact-absorbent topcoat layer of resinous copolymeric materials. This process first seals the asbestos in a hard, abrasive and brittle material which is then covered by a resinous coating to protect both the asbestos encapsulant and workers who may otherwise come into contact with the abrasive encapsulate. Unfortunately, this material may fracture when it is subjected to mechanical and thermal stresses such as foot traffic, widely fluctuating temperatures, thereby releasing asbestos particles into the atmosphere. The process also requires multiple application steps in order to provide more permanent control of asbestos particles. This is a time consuming process and often renders the workplace unusable for an extended period of time while the composition dries or cures to a sufficient degree. The topcoat does not have the capability to be used directly over soil, and it is not recommended for such a use.
Workplaces having dirt floors also provide conditions promoting the growth of microorganisms such as bacteria and fungi. These organisms can attack and seriously degrade organic compositions often used to encapsulate or bridge asbestos containing material. Some of the products of the prior art also provide only temporary encapsulation or bridging of the asbestos with the material. If the bridged dirt floor is subjected to heavy traffic, the encapsulating material may also be severely broken down through tearing stress, impact and abrasion.
Based on the current state of the art, an easily applied permanent, tough and durable coating resistant to microbial degradation is needed for bridging asbestos containing soil to prevent asbestos particles contained within from becoming airborne. A tough, quick-forming coating is also needed which can allow the rapid reuse of a workplace after the application of the coating.